Innovation is an imperative in all industry sectors. For those such as construction, which are not considered high-tech and which operate as one-off projects, the uptake and diffusion of new innovations into ongoing practice across projects pose particular problems. The nature of these problems faced at a project level needs to be better understood. This thesis is an exploration of innovation implementation in the context of Project-Based Engineering (PBE). It is an empirical investigation of how new planning technologies are implemented in major infrastructure construction projects and the barriers that prevent such implementations from being effective. The findings of this investigation are used to develop and evaluate a new model of innovation implementation in this context. The research design is centred on the immersion of a participant-observer in seven live construction projects over a period of 3.5 years. Each project studied was implementing the same innovation: 4D CAD modelling (3D design model + the construction schedule). A wide cross-section of data was gathered in the field including direct observations, documents and other work products from participation, email and other correspondence associated with the 4D CAD implementations, and formal and informal discussions with project-participants. These data were analysed using content analysis software to find patterns. The research was iterative and involved three phases. The initial phase was a pilot study of implementation in practice using the data from one project. It produced rich descriptions of what transpired and a critical comparison with accounts from the literature. This led to a series of propositions about the influence of project-participant perceptions that were synthesised into a new theoretical model: the initial Perception-Influence model (P-I1 model). The middle research phase then developed this model iteratively using a more-focused data collection and content analysis across four construction project organisations. This was done to provide supporting evidence for the theoretical constructs in the P-I1 model as well as to refine them and add new ones. The outcomes of the middle phase were the P-I2 and P-I3 models. The final research phase analysed the data from the last two project organisations in terms of the P-I model framework with a view to evaluating the model’s theoretical significance and practical applications. The P-I model shows that negative perceptions of value, benefit and usability can cause an innovation implementation to be ineffective as a result of discontinued use or neglect. It provides a map for the progression of an implementation using the perceptions and actions of project-participants as primary constructs. The model proposes that each perception is formed by a number of contributing factors or secondary constructs synthesised from implementation research and user acceptance literature, for example, an opinion or concern about how much an innovation costs (i.e. transaction costs). It also proposes that each perception has both a positive and negative associated action. The constructs that make up the P-I model are grounded in the empirical data. This is because the actions, opinions and concerns of project-participants observed in live projects are evident in project documentation such as emails. These two sources (i.e. observations and project documentation) provide data sets that were used to triangulate inferences about the perceptions of project-participants and the outcome of each 4D CAD implementation (i.e. effective or otherwise). This aspect of the research was not only important for the recommendation of potential applications for the P-I model but also during its conception, development and evaluation. The P-I model is a new and important perspective for both implementation research and PBE practitioners. It helps satisfy the calls for studies of innovation implementation that focus on factors at an individual level and those asking for a better understanding of innovative behaviour. This work shows PBE practitioners how the perceptions of project-participants can have a major impact on the effectiveness of an innovation implementation. The findings provide an evidential basis that can improve implementation effectiveness, especially in PBE organisations. The knowledge built into the P-I model can also assist the planning and execution of innovation implementation strategies, aid in the assessment and redirection of those in progress, and help document lessons learned for implementations within project organisations that have been previously completed. This research uses the P-I model to open the way for future empirical studies of innovation implementation in PBE contexts beyond construction. These would also provide data to further refine the constructs in the model.